The use of radiation to treat medical conditions comprises a known area of prior-art endeavor. For example, radiation therapy comprises an important component of many treatment plans for reducing or eliminating unwanted tumors. Unfortunately, applied radiation does not discriminate between unwanted materials and adjacent tissues, organs, or the like that are desired or even critical to continued survival of the patient. As a result, radiation is ordinarily applied in a carefully administered manner to at least attempt to restrict the radiation to a given target volume.
Collimators are often used to restrict and form the radiation-therapy beam. Some collimators have an aperture that can be adjusted in one or more dimension. Adjustable apertures permit, to at least some degree, customization of the radiation-therapy beam's cross section to thereby attempt to better match the requirements of a given target volume. Multi-leaf collimators are an example of such a component. Multi-leaf collimators are comprised of a plurality of individual parts (known as “leaves”) that are formed of a high atomic numbered material (such as tungsten) that can move independently in and out of the path of the radiation-therapy beam in order to selectively block (and hence shape) the beam.
Many treatment plans provide for exposing the target volume to radiation from a number of different directions. Arc therapy, for example, comprises one such approach. In such a case it often becomes useful or necessary to adjust the multi-leaf collimator to accommodate various differences that occur or accrue when moving the radiation source with respect to the target volume. A radiation-treatment leaf-sequence plan provides information regarding useful or necessary adjustments to the multi-leaf collimator(s) at numerous sequential positions during such a treatment.
Optimizing such a plan can prove challenging. Amongst other things, the radiation target may not be located, shaped, or sized at the time of administering a treatment dosing as was thought to be the case when forming and optimizing the radiation-treatment leaf-sequence plan. To accommodate such a circumstance it is known to plan for dynamic modifications to a given radiation-treatment leaf-sequence plan to thereby attempt to adapt to a patient's presentation at the time of administering the corresponding treatment.
Though helpful to an extent, such a practice sometimes gives rise to one or more new problems. As one example in these regards, a particular planned or theoretically-available modification with respect to the stipulated position of one or more leaves of a multi-leaf collimator may be impossible to achieve due to one or more corresponding physical limitations. For example, a given leaf may simply not have enough time to reach a modified position before the treatment process must continue. This, in turn, can render a planned or accommodated modification theoretically interesting but practically unhelpful.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.